Telephone receiver



July 27 192 1,593,556

P.G.ANDRES TELEPHONE RECEIVER Filed Deq.13. 1922 'Imrsn Err- Paul EfinuEzes Patented July 27, 1926.

UNITED STATES PATET F F l C E.

IPA UL G. ANDRES, OF RIVER FOREST, ILLINOIS, ASSIGNOR, BY MESNE ASSIGNMENTS,

TO AUTOMATIC ELECTRIC INC., OF CHICAGO, ILLINOIS,

WARE.

A CORPORATION OF DELA- TELEPHONE RECEIVER.

Application filed December 13, 1922.

My invention relates in general to telephone receivers and particularly to an improved magnetic construction therefor.

Among the objects of the invention are; to provide a novel magnetic construction of a receiver having a leakage or shunt path of low reluctance for the magnetic flux generated by voice currents in the coil thereof; to provide a single center coil receiver of high efiiciency; to provide a permanent magnet receiver in which the permanent magnet will retain its magnetism, and the receiver its efficiency regardless of a direct current flow therethrough in either direction; to provide a non-ferrous metallic shield in order that changes of flux in the permanent magnet may not afiect the diaphragm, and to provide other details of improvement in the construction of a receiver which tend toward high efficiency in operation and low cost of manufacture.

In the accompanying drawings, Fig. 1 is a front view of the receiver with the cap and diaphragm removed.

Fig. 2 is a front view of the receiver with the cap, diaphragm and non-ferrous metallic shield removed.

Fig. 3 is a sectional view of the receiver shown in Fig. 1 looking in the direction of the arrows along the line AA.

Fig. 4 is a diagrammatical illustration of the magnetic principles of the invention.

Fig. 5 is a view of one of the receiver pole pieces bearing the extension which Very nearly but not quite encircles the magnet coil.

Fig. 6 is a view of the other pole piece showing the core of the magnet coil.

As illustrated in the drawings, it will be seen that the improved receiver comprises the horseshoe permanent ma net 12 mounted in the usual casing 10. finder one pole of the magnet 12 is the soft iron part 13 which forms an extension of one pole of magnet 12. A soft iron part 14 is placed under the pole of magnet 12 opposite part 13, this part 14 carrying a stud 22 in the center of the receiver which forms the core of a coil 15, having insulating washers 16 there on to hold the winding of the coil in place.

A block of insulating material 17 is placed between the poles of the magnet 12 to serve as a terminal block. This block 17 carries a pair of screws 18, each of which hold a terminal of the coil 15 and to which the ends Serial N 0. 606,593.

of the usual receiver cable may be connected as shown m Fig. 1.

The non-ferrous metallic shield 19 rests 'upon the upper surface of both the permanent magnet 12 and the insulating material 17, and by means of the screws 20, serves to clamp the entire assembly to the casing 10.

The diaphragm 21. of the usual type is held in place across the top edge of the easing 10 by means of a cap 11 of insulating material which is threaded upon the rim of the casing 10.

A'detailed view of one of the pole pieces is 1 shown in Fig. 6 and from this figure it will be noted that on this pole piece is riveted the 7 pin 22. Upon this pin is wound the electromagnet 15. A detailed view of the other pole piece is shown in Fig. 5, and from this it will be seen that the pole piece 13 is so formed that when the receiver is assem- 7 bled this pole piece will nearly but not quite encircle the-coil which is wound on the extended portion of the pole piece 14. This structure is clearly shown in Figs. 2 and 3. There is a small air gap between the two pole pieces beneath the coil when assembled, as may be seen at reference character 23, which greatly increases the eiiiciency of the receiver, as will be explained fully hereinafter.

Having described the mechanical construction of the improved receiver, its theory of operation will now be gone into by reference to Fig. 41. The magnetic circuit of the permanent magnet 12 includes the pole piece 14, the core 22, the diaphragm 21 and the pole piece 13. A certain amount of leakage fiux of course will follow the gapbetween the pole pieces, as indicated by reference character 23, without passing through the diaphragm 21, the reluctance of this gap being made equal to the reluctance through the diaphragm. The effect of the varying magnetic flux produced by the voice currents in the coil of the electromagnet are localized in the pole pieces; that is, the flux generated by the coil is set up in the following circuit: the pole piece 1 1, core 22", diaphragm 21, pole piece 13 and the gap 23. This magnetic circuit is made up of soft iron having high permeability and does not include the permanent magnet which is of hard steel having a relatively low permeability. The non-ferrous metallic shield 19 effectively prevents any action of the diaphragm in response to changes in the flux occurring in the permanent magnet. In a receiver of this design it does not mat-.

ter whether it be poled so that the directcurrent 511C115 or opposes the permauentmagnettlux as the maximum deflection of the" diaphragm will always occur at the cent-er, and when alternating current is impressed the diaphragm is deflected as a unit. -Due to the air gap 23 the alternating flux may flow without causing demagnetization of the permanent magnet.

The structure or this receiver whereln'pole pieces of sott'iron constitute the main part of the magnetic circuit which is subject to the rapid variation of magnetism produced by alternating currents is very advantageous and this construction produces a most eflicientreceiver. Other advantages lie in the arrangement whereby a single coil exerts an attractive force upon the'center of the-dis phragm, together with the introduction of -a shield which causes the diaphragm to be unaffected by changes in the permanent magnet flux, and also in the construction of the I pole pieces so that thereis uniform pull on 1. In a telephone receiver, a cylindrical "casing clo'sed at one posed pole pieces at the bottom of said casing, a permanent horseshoe magnet having its'poles resting on said pole pieces, a semicircular terminal block occupying the space end, two radially disbetween the poles of said magnet,said block having its upper surface substantially flush with the top side of said magnet, andanonmagnetic circular plate fitting in said casing above the magnet and block and secured to the bottom of the casing to clamp the several parts together.

2; In a telephone receiver, a casing, apermanentmagnet-inside said casing, two fan shaped pole pieces having their wide ends clamped between the poles of said magnet and the bottom of the casing, a magnet coil having its COlGSllPPOItGCl at the apex of one pole piece, a split cylinder supported at the apex of the other pole piece and surrounding said 'coil', and a diaphragm-supp'orted adjacent the free ends of said cylinder and magnet core.

3." In a telephone receiver, a casing, a permanent magnet-soft iron pole pieces for said magnet, one of said pole pieces being provided with an extension at rightangles'to it and having a coil wound thereon, the other pole piece having a tubular projection positioned'so that it encloses the said coil, and a non-magnetic metal disk surrounding said tubular pole piece and lying in a plane parallel to the base of said casing.

' ii In a telephone receiver, a casing, a permanent magnet, soft iroir polev pieces for said magnet, one of said pole pieces being provided with an extension at rightanglesto itand having a coil wound thereon, the other pole. piece having a tubular extension positioned so that it encloses-the said coil, a =no1r-magnetic metal disk surrounding said tubular pole piece and lying in a plane parallel to'the base of said casing, and screws extending through onlythe said plate and easing effective to cause said plate to firmly hold said magnet and pole pieces in place.

5. In a telephone receiver, an imperforate permanent magnet enclosed in a cup shaped casing, a diaphragm clamped on said casing parallel to said magnet soit iron'polepieces torsaid magnet one of which contains a 0011 carrying projection locatedbe'neath the center of the diaphragm, acylindrical projection on said other pole piece which encircles said coil and which isseparated from said first pole piece .by a small air gap, a nonmagnetic disk encircling said projections and resting on said magnet and means engaging onlysaid disk and casing for clamping the several parts together.

In witness whereo'L I hereunto subscribe my name this 11th 'day of December, A. D.

" PAUL G. ANDRE 

